1. Field of the Invention
This invention relates to halogenated phosphoric esters and to flame-proofing compositions for polymeric materials such as polyurethanes and polyesters, based on such halogenated phosphoric esters.
2. The Prior Art
It is, of course, known that to improve the flame resistance of polymeric materials, flame-proofing additives, i.e., products which are capable of rendering the polymeric materials fire-proof or self-extinguishing or at the very least, capable of reducing the combustion rate thereof are added to the polymeric materials.
For some time now, certain halogenated phosphoric esters have been proposed for utilization as flame-proofing additives for polymeric materials of various types, including particular polyesters and polyurethanes.
It is known that polyurethanes, to which have been added certain of the known halogenated phosphoric esters, while exhibiting good flame resistance characteristics, may sometimes be subject, after ageing, to mechanical and thermal degradation phenomena, which seriously limit the practical utilization of such treated polyurethanes.
Moreover, certain of the known halogenated phosphoric esters, when incorporated into polyurethanes tend somehow to migrate towards the outside of the material into which they had been incorporated and then to volatilize therefrom, as a result of which their permanence characteristics are not completely satisfactory.
Accordingly, it is an object of the present invention to provide halogenated phosphoric esters suitable for use as flame-proofing additives for various types of polymers and which are free of the above-mentioned disadvantages.